News & Events

Novel Terahertz Metamaterials

Dr. Antoinette J. Taylor, Los Alamos National Laboratory

Monday, November 18, 20133 p.m.4:30 p.m.Sloan Auditorium

Abstract:Electromagnetic metamaterials are structured composites with
patterned metallic sub-wavelength inclusions. These mesoscopic systems are
built from the “bottom up”, at the unit cell level, to yield specific
electromagnetic properties. Individual components respond resonantly to the
electric, magnetic, or both components of the electromagnetic field. In this
way electromagnetic metamaterials can be designed to yield a desired response
at frequencies from the microwave through the visible. Importantly, additional
design flexibility is afforded by the judicious incorporation of naturally
occurring materials within the active region of the metamaterial elements. Specifically,
hybrid metamaterial composites result when the properties of a natural
material, e.g. semiconductors or complex oxides strongly couple with the
resonance of a metamaterial element. The resulting hybrid metamaterials will
still exhibit “passive” properties (e.g. negative electric response, negative
index, gradient index, etc.), as determined by the patterning of the
metamaterial elements. However, the aforementioned coupling engenders control
of the passive metamaterial response via external stimulus of the natural
material response (photoconductivity, nonlinearity, gain, etc.).

In recent years
terahertz (1 THz = 1012 Hz) technology has become an optimistic candidate for
numerous sensing, imaging, and diagnostic applications. Nevertheless, THz technology
still suffers from a deficiency in high-power sources, efficient detectors, and
other functional devices ubiquitous in neighboring microwave and infrared
frequency bands, such as amplifiers, modulators, and switches. One of the
greatest obstacles in this progress is the lack of materials that naturally
respond well to THz radiation. The potential of metamaterials for THz
applications originates from their resonant electromagnetic response, which
significantly enhances their interaction with THz radiation. Thus,
metamaterials offer a route towards helping to fill the so-called “THz gap”.

Here, I
will present metamaterials with designed novel and/or active functionality,
enabling control and tuning of the amplitude, frequency and polarization state
at THz frequencies1-10. In many of these materials the critical dependence of
the resonant response on the supporting substrate and/or the fabricated
structure enables the creation of active THz metamaterial devices. We show that
the resonant response can be controlled using optical or electrical excitation
and thermal tuning, enabling efficient THz devices that will be of importance
for advancing numerous real-world THz applications.